1. Field of the Invention
While the self-propelled dual-jack hoist of my U.S. Pat. No. 3,817,401 was quite successful in use, it appeared--with continued development--that faster performance, improved maneuverability, and increased stability, together with certain additional functions, were desirable in a hoist of the type, and for the purpose, described. The present modification of the hoist was conceived by me in a successful effort to provide such improvements.
2. The Prior Art
My identified U.S. Pat. No. 3,817,401 is the most relevant prior art known to me, while other known prior art--beyond the references cited in the file of such patent--is represented by the following U.S. patents:
U.s. pat. No. 2,471,901 PA1 U.s. pat. No. 2,480,916 PA1 U.s. pat. No. 2,533,980 PA1 U.s. pat. No. 3,761,040.
The above prior art--considered singly or together-- does not anticipate, nor suggest as obvious, the particular structure of the herein-claimed crawler-type self-propelled hoist, and applicant has no knowledge of any prior art disclosing such particular structure.